(a) Field of the Invention
The present invention is related to a localized surface plasmon resonance (LSPR) sensing system with noble metal nano-particles on an optical fiber as a transducer, and more particularly, to a LSPR sensing system, apparatus, and method thereof.
(b) Description of the Prior Art
Propagated surface plasmon resonance (PSPR) relates to a phenomenon when an incidence light emitted from a light source reaches the surface of the metal film at a fixed incident angle, the light intensity reflected from a surface of the metal film picked up by a photo detector is approaching zero, i.e., the reflectance of the metal film is approaching zero while the light beam not reflected propagates at a given speed in a direction along the interface and excites the plasmon on the surface of the metal film to resonate. However, light in the sample medium cannot naturally excite PSPR and a high refractive index prism or grating is required for coupling.
The PSPR sensing system is provided according to the PSPR phenomenon described above by having the surface of a prism or a grating coated with a layer of metal film and then the recognition molecule of an analyte is immobilized or attached to the surface of the metal film. Once the analyte in a sample binds with the recognition molecule, the PSPR phenomenon will be undergoing a certain change that reveals and thus detects the interaction status between the recognition molecule and the analyte.
Since the PSPR sensor has high sensitivity and is label-free, thus it allows real-time analysis of interaction between the recognition molecule and the analyte, and furthermore, permits rapid, quantitative, and parallel screening. The PSPR sensor has been widely applied to detection of bio-molecules.
While the development of nano-materials has been becoming a focus of studies in recent years, optoelectronics, communication, and medical instruments are included in the studies because nano-materials have properties totally different from those bulk materials. In this regard, localized surface plasmon resonance (LSPR) sensing system via excitation of noble metal nano-particles when compared with the conventional propagating surface plasmon resonance (PSPR) sensing system may offer additional advantages such as shorter electromagnetic field decay length, smaller pixel size, faster response time, and capability of simultaneous LSPR sensing and surface-enhanced Raman scattering. Moreover, because PSPR is an extrinsic resonance phenomenon, the PSPR sensor requires complicated optical setup and is bulky in size and thus is difficult to be miniaturized and expensive to afford. Today, the roadmap for the development of biosensor is heading for a miniaturized design. Should the biosensor be made in smaller size for easy portability and simpler design of detection method and operation performance, its applications could have been significantly extended.